1. Technical Field
The present invention relates to spark plugs for igniting the fuel/air mixture in a combustion chamber of an automobile and to systems and methods for reducing corrosion, clogging and fouling of the center electrode of the spark plug.
2. Discussion
Spark plugs, of course, are well known in the automotive and other industries for igniting the fuel mixture in the cylinders of internal combustion engines. Spark plugs are exposed to extremely high temperatures and corrosive environments which reduce their useful life. In order to increase the useful life of the spark plug, and especially the discharge portion of the spark plug, many spark plugs use metals containing predominately Platinum (Pt), Iridium (Ir) or alloys thereof. Nonetheless, corrosion mechanisms are still present with spark plugs using Ir. The corrosion mechanism on spark plugs using Ir occurs through the presence of calcium and/or phosphorus, both of which are often present in the oil used to lubricate the engine, which invariably enters the combustion chamber in internal combustion engines. Due to the high temperature of the combustion reaction it has been found that calcium and phosphorous may wear away or corrode the Ir on the electrode of the spark plug. Other problems with Ir include severe oxidation at certain temperature ranges. Though the discharge portion of the spark surface is typically immune from wear, over time corrosion or oxidation may cause pieces of the discharge portion to dissolve, erode and/or vaporize. It is believed that calcium and/or phosphorus is the cause of this wear. The source of the calcium and phosphorus is from the lubricating oil that is circulated throughout the engine. A small amount of lubricating oil is present in the combustion chamber as it moves past the piston rings.
Engine designers and manufacturers are continually pressured to increase the efficiency of the engine. One major source of loss of efficiency is in the form of friction. Major friction losses occur through the reciprocal movement of the pistons within the combustion chambers. In an effort to reduce the friction between the pistons and combustion chamber walls, engine designers are changing the piston ring designs to reduce friction, which tends to allow more oil to pass between the piston and combustion chamber walls, thus leading to an increase of engine lubricant entering into the combustion chamber. This increase in engine lubricant into the combustion chamber increases corrosive compounds, such as calcium and phosphorus, and exacerbate the corrosion and fouling of the Ir containing electrodes.
Further, it has been observed that during the combustion cycle, calcium and phosphorus is present in ionic form in the gas phase of the combustion cycle. The gas containing the calcium and phosphorus molecules condenses into a liquid onto the tip of the Ir electrode. Because the calcium and phosphorus ions are positively charged, they are attracted to the negatively charged electrode of the spark plug. Once on the tip of the electrode, the corrosion mechanism of the calcium and phosphorus ions acts to corrode and/or foul the electrode. Moreover, it is known that molten calcium dissolves Ir and leaves the Ir electrode vulnerable to oxidation.
Therefore, there is a need for a new and improved method and system for preventing or reducing the corrosion mechanism caused by the presence of calcium and phosphorus in the combustion chamber.